A new herbicide mixture: bispyribac sodium+metamifop 14% SE for weed control in wet seeded rice

Abstract

In direct seeded rice (DSR), weeds are the major biotic constraint in improving the productivity of rice. Acute labour shortage and hike in wage rate force the farmers to rely more on herbicides for weed management in DSR. But the continuous use of same herbicide or herbicides with similar mode of action leads to shift in weed flora and resistance development in weeds. One of the ways to overcome these problems is the use of herbicide mixtures. Hence, field experiments were conducted for two seasons kharif 2014 and rabi 2014–15 to assess the bio-efficacy of bispyribac sodium+metamifop, a post-emergence herbicide mixture for broad spectrum weed control in DSR. The experiment was laid out in randomized block design with seven treatments and three replications. The treatments comprised four doses of bispyribac sodium+metamifop viz., 60, 70, 80 and 90 g/ha, bispyribac sodium @ 25 g/ha, hand weeding twice and weedy check.Schoenoplectus juncoides, Cyperus iria, Cyperus difformis, Fimbristylis miliacea, Isachne miliacea, Ludwigia perennis, Limnocharis flava, Sphenoclea zeylanica, Marsilea quadrifolia, Bergia capensis, Commelina diffussa and Monochoria vaginalis were the major weeds in the experimental field. Among the three morphological groups of weeds, sedges was the most predominant one in the experimental site. Results revealed that compared to bispyribac sodium @ 25 g/ha, bispyribac sodium+metamifop @ 70, 80 and 90 g/ha was found more effective in reducing the density and dry weight of weeds. Application of bispyribac sodium+metamifop @ 90 g/ha registered the highest weed control efficiency of 96.62%. Grain yield was also significantly influenced by the weed control treatments. The highest grain yield (8051 kg/ha) and net returns (Rs. 86238/ha) were recorded in bispyribac sodium+metamifop @ 90 g/ha and it was statistically comparable with the lower doses of 80 and 70 g/ha. Bispyribac sodium+metamifop @ 90, 80 and 70 g/ha was significantly superior to hand weeding twice and bispyribac sodium applied @ 25 g/ha in terms of net returns and B: C ratio.